The Application of Resonance Ultrasound Spectroscopy to Bearing Rollers

If we apply continuous sweep of vibrational frequencies to a solid, the object will resonate, or ring just like a bell, provided the applied sound frequency matches one of the samples natural vibrational frequencies. The resonances of a solid are affected by its elastic properties, shape, size and density. Any deviation, from the ideal, (crack, grinding burn, dent, dimensional change, hardness difference…) changes the resonance spectrum. This technique is being used to rapidly sort axially symmetric roller bearing elements containing any of several flaws, independent of part orientation. The flaws of concern include: cracks (down to 1mm × 50 μm), dimensional and hardness deviations. Industrial bearing manufacturers have found that RUS was able to reliably find cracks which were missed by Eddy Current, whether the defects occurred on the body or end, and without appreciable false rejects. Simultaneous with crack examinations, RUS is able to measure the length of 15 mm tapered rolling elements to ±5μm. Specific data on crack determinations along with dimensional measurements will be presented.